Soi substrate and method for manufacturing the same

Abstract

To provide an SOI substrate having a high mechanical strength, and a method for manufacturing the SOI substrate, a single crystal semiconductor substrate is irradiated with accelerated ions so that an embrittled region is formed in a region at a predetermined depth from a surface of the single crystal semiconductor substrate; the single crystal semiconductor substrate is bonded to a base substrate with an insulating layer interposed therebetween; the single crystal semiconductor substrate is heated to be separated along the embrittled region, so that a semiconductor layer is provided over the base substrate with the insulating layer interposed therebetween; and a surface of the semiconductor layer is irradiated with a laser beam so that at least a superficial part of the semiconductor layer is melted, whereby at least one of nitrogen, oxygen, and carbon is solid-dissolved in the semiconductor layer.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a substrate in which a single crystal semiconductor layer is provided on an insulating layer, and a method for manufacturing the substrate. In particular, the present invention relates to an SOI (silicon on insulator) substrate and a method for manufacturing the same. Furthermore, the present invention relates to a semiconductor device formed using an SOI substrate and a method for manufacturing the same.[0003]2. Description of the Related Art[0004]In recent years, devices such as semiconductor integrated circuits, which use an SOI substrate including a thin single crystal semiconductor layer formed on an insulating surface, have been developed instead of those using a bulk silicon wafer. Since the parasitic capacitance between a drain of a transistor and a substrate is reduced by using an SOI substrate, SOI substrates have attracted attention as substrates for improving the performance ...

AI Technical Summary

Benefits of technology

[0012]A single crystal semiconductor ingot or a single crystal semiconductor wafer manufactured by the CZ method contains oxygen at a concentration of 1×1017 atoms / cm3 to 1×1018 atoms / cm3, and the concentrations of nitrogen and carbon are 4×1015 atoms / cm3 or less and 2×1016 atoms / cm3 or less, respectively, even though they are added intentionally. The impurity concentration in a single crystal semiconductor ingot manufactured by the FZ method is generally lower than that in a single crystal semiconductor ingot manufactured by the CZ method; therefore, the single crystal semiconductor ingot manufactured by the FZ method has a problem of a poor mechanical strength to be easily broken. On the other hand, since the impurity concentration in bulk silicon manufactured by the CZ method is higher than that in bulk silicon manufactured by the FZ method, bulk silicon manufactured by the CZ method has a higher mechanical strength.

[0039]When at least one element of nitrogen, oxygen, and carbon is contained in a single crystal semiconductor layer formed on an insulating surface at a predetermined concentration, the mechanical strength of an SOI substrate having the single crystal semiconductor layer can be improved. Furthermore, generation of voids in the single crystal semiconductor layer can be suppressed.

Problems solved by technology

In the case where a large-sized device such as a display or a device having a curvature is formed using, for example, a single crystal silicon layer formed on an insulating substrate such as a glass substrate as disclosed in Patent Document 2, a poor mechanical strength of the single crystal silicon layer due to its reduced thickness has been a problem.

The poor mechanical strength of the single crystal silicon layer with a reduced thickness might cause cracks and breaking of the single crystal silicon layer in the manufacture or use of the device.

In addition, there has been a problem in that linear defects (dislocations) or planar defects occur or grow, and even when a transistor is formed using the single crystal silicon layer, characteristics of the transistor are deteriorated.

The impurity concentration in a single crystal semiconductor ingot manufactured by the FZ method is generally lower than that in a single crystal semiconductor ingot manufactured by the CZ method; therefore, the single crystal semiconductor ingot manufactured by the FZ method has a problem of a poor mechanical strength to be easily broken.

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